Timing chain drive comprising an integrated electric motor

ABSTRACT

The invention relates to a timing drive for an internal combustion engine, comprising a crankshaft, at least one camshaft, a driven gear that is connected to the crankshaft, at least one driving gear which drives the associated camshaft and a transmission that interconnects the driven gear and the at least one driving gear. An electric motor is provided which engages with the transmission in an offset manner relative to the crankshaft and the at least one camshaft as well as in an offset manner relative to the associated driven gear and the associated at least one driving gear by means of an intermediate gear. Furthermore, a control device is provided, with the aid of which the electric motor can be triggered in such a way that additional torque and/or an additional torque profile can be introduced into the transmission and/or can be tapped from the transmission based on at least one operational parameter and/or at least one operational situation of the transmission. Also disclosed is a corresponding method.

The present invention relates to a timing drive for an internal combustion engine, comprising a crankshaft, at least one camshaft, a driven gear that is connected to the crankshaft, at least one driving gear which drives the associated camshaft, and a transmission that interconnects the driven gear and the at least one driving gear.

Particularly in the last decade, numerous measures have been taken in order to develop internal combustion engines in a manner that is quieter with respect to their running characteristics. Timing drives should also run smoothly and with as little noise as possible. If flexible means of wrapping, such as chains and belts, are used in timing drives, special tensioning devices and guidance means are provided so that the timing drive can run as quietly as possible. When timing chains are used, a tendency toward toothed chains can also be seen, because these further contribute to reducing noise. In the case of the transmission that interconnects the driven gear of the crankshaft and the driving gear of the crankshaft or the driving gears of the crankshafts, it can be a belt transmission, a chain transmission or a gear transmission, or a mixture of these design alternatives.

The object of the present invention is to open a timing drive of the type mentioned at the beginning to newer development possibilities and nevertheless improve the service life in normal operation.

This object is solved according to the invention in that an electric motor is provided which engages with the transmission in an offset manner relative to the crankshaft and the at least one camshaft as well as in an offset manner relative to the associated driven gear and the associated at least one driving gear by means of an intermediate gear, and in that a control device is provided, with the aid of which the electric motor can be triggered in such a way that additional torque and/or an additional torque profile can be introduced into and/or tapped from the transmission based on at least one operational parameter and/or at least one operational situation of the transmission. Due to the arrangement and the engaging of the intermediate gear, it can also be said that the electric motor is integrated into the transmission. The transmission is accordingly defined without crankshaft, driven gear and camshaft(s) and driving gear or driving gears. This means that the at least one operational parameter or the at least one operational situation reflects the condition or situation of the transmission. In contrast to this, measures that are intended to balance out the rotational nonuniformity of the crankshaft are best known. If these nonuniformities are also transmitted to the transmission, the effects within the transmission are, however, completely different than those on the crankshaft itself. If one were to imagine a simplified picture of the timing drive with crankshaft and at least one camshaft as a large mass (crankshaft), small mass (crankshaft(s)) and the transmission as a spring that interconnects these, it can easily be seen that the conditions in the spring system are completely different than those involving the two masses. Measures that affect the camshaft are likewise known. Given as examples here are DE 442577 A1, DE 19532129 A1, DE 19939605 A1 and JP 2002-309961A. The known measures, however, leave out the operational situation and operational states of the transmission, and selective engaging in the transmission by means of the electric motor, depending on these operational conditions, is unknown until now. The additional electric motor consequently directly influences the timing drive by engaging with the transmission. By both introducing and tapping torque, the electric motor changes the “transmission” vibration system, as a result of which it selectively influences this dynamic system due to the controlled engagement via the control device. Directly engaging in the transmission appears disadvantageous at first glance, but this takes place offset to the crankshaft and to the camshaft or camshafts, so that the electric motor influences the crankshaft and the camshaft or camshafts only indirectly via the transmission that engages with them. A part of the transmission consequently lies as a buffer element between the crankshaft and the camshaft or camshafts.

Furthermore, a registering device and/or evaluation device can be provided, by means of which the at least one operational parameter and/or the at least one operational situation of the transmission can be registered and/or evaluated, wherein the vibration state of the transmission is registered and/or evaluated as an operational parameter and/or the vibration situation of the transmission is registered and/or evaluated as an operational situation.

In this way, vibrations that arise in the transmission can be reduced by an induced vibration directed against them, and the formation of resonances can be prevented. For this purpose, magnitudes can be directly registered or evaluated on the basis of the known characteristics, e.g., by means of the engine characteristics. The transmission's resonances that occur are known ahead of time. This function furthermore allows optional downsizing of the timing drive components.

The invention according to one variant has a particularly advantageous effect in the case of transmissions with flexible means of wrapping. In one variant, the transmission has at least one timing chain for this purpose. Timing chains tend to vibrate easily, which is why suitable measures that introduce and tap torques bring good improvement here.

The intermediate gear can furthermore engage with the at least one timing chain. The engine is consequently directly coupled to the timing chain.

Timing chains in which the crankshaft sprocket is connected directly to the cam wheel or cam wheels via a simplex or duplex timing chain can be used. Other design variants provide for a first timing chain to be connected to an intermediate shaft sprocket, which has two ring gears. The second ring gear, which is not engaged with the first timing chain, drives a second timing chain, which is guided around the camshaft gear or the camshaft gears. In such a development, it is also possible for various divisions of the timing chains to be used. In addition, it is possible to create a gear ratio that leads to more favourable conditions between the crankshaft sprocket and the camshaft sprocket or camshaft sprockets. The intermediate shaft can also be used to drive an auxiliary unit.

According to one design variant, an intermediate shaft is provided that is in an effective connection with the crankshaft by means of a first timing chain and with the at least one camshaft by means of a second timing chain, wherein the electric motor engages directly with the intermediate shaft. The intermediate shaft could furthermore also be drawn on to drive an ancillary component, e.g., a high-pressure pump. This variant also makes conversion possible between the crankshaft sprocket and the camshaft sprocket or camshaft sprockets. This allows the number of teeth in the individual sprockets to be optimised. Due to the relatively short chain lines up to the intermediate shaft sprocket, the electric motor can also exercise a more favourable influence on the overall characteristics of the timing chain drive by introducing and/or tapping a torque.

At the same time, a rotor shaft of the electric motor can preferably be formed as an intermediate shaft or be connected to it coaxially, as a result of which there is a very compact arrangement in the area of the intermediate shaft. The arrangement at the intermediate shaft furthermore has the advantage that the electric motor can be arranged offset and next to the actual engine block, so that only the rotor shaft of the electric motor is led into the timing chain shaft or chamber, which is filled with oil. The electric motor can easily be sealed off from the oil that moistens the timing chain drive because only the rotor butt that engages in the oil chamber has to be sealed off. The entire stator of the electric motor can be placed outside the oil chamber. The stator can consequently extend alongside the engine block, as a result of which the internal combustion engine does not have to be longer than comparable internal combustion engines without an electric motor.

The control device can furthermore be developed as a regulating device and the electric motor can be regulated by the regulating device in such a way that additional torque and/or an additional torque profile can be introduced into the transmission and/or tapped from the transmission in a regulated manner by means of the electric motor. This should accordingly be a closed loop, which requires that control variables be measured, so that the additional torque and/or torque profile can be readjusted in the framework of a closed loop. Depending on the time delay of the closed loop, there consequently results an essentially direct adjustment to the respective operating conditions.

In addition to this, it can be provided that the regulating device is connected to a sensor device, by means of which at least one signal that depends on an operational parameter and/or an operational situation of the transmission can be registered and passed on to the regulating device, wherein the electric motor can be regulated by means of the regulating device in such a way that additional torque and/or an additional torque profile can be introduced into the transmission and/or tapped from the transmission by means of the electric motor depending on the operational parameter and/or the operational situation. Here it is consequently possible to register one or more magnitudes that influence the timing chain drive and allow this magnitude or these magnitudes also to play a role in influencing the control for the electric motor. The operational parameters are advantageously determined during operation of the internal combustion engine and are not standstill magnitudes.

In a further development, the electric motor is formed as a starter motor for the internal combustion engine. Starting is accordingly handled via the transmission. Due to the high level of robustness of, e.g., a timing chain, this is easily possible and consequently avoids additional design effort.

The invention furthermore relates to a method for operating a timing drive on an internal combustion engine, whereby in said method, an electric motor, in an offset and separate manner relative to the crankshaft and at least one camshaft, as well as in an offset manner relative to the associated driving gear and the associated at least one driven gear, is integrated into a transmission that interconnects the driving gear and the at least one driven gear, and can be triggered by means of a control device in such a way that additional torque and/or an additional torque profile can be introduced into and/or tapped from the transmission by means of the electric motor. The method comprises the following steps:

Registering of at least one operational parameter and/or one operational situation of the transmission; Triggering of the electric motor by means of the control device, in order to introduce into and/or tap from the transmission additional torque and/or an additional torque profile, depending on the at least one operational parameter and/or operational situation.

Such a method opens up diverse possibilities for improving a timing drive. For example, vibrations that arise in the timing drive can be reduced by directing induced vibrations against them by means of the electric motor, and formation of resonances can be prevented. Since vibrations play an important role in the design of timing drive components, downsizing measures can also be carried out that lead to a reduction in the cost of this series product. In addition, reduced vibrations also allow an improvement in the cam valve lift characteristics, as a result of which there are also improvements outside the timing drive.

Furthermore, at least one operational parameter that implies the vibrations that occur in the transmission and/or that, as an operational situation, implies the vibration situation of the transmission, can be registered and/or evaluated and the control device can trigger the electric motor in order to introduce into and/or tap from the transmission additional torque and/or a torque profile, depending on the at least one operational parameter and/or operational situation for vibration absorption. Such an operational parameter accordingly directly or indirectly suggests the vibration state of the timing drive. The advantages that result due to this method variant are already explained above.

Furthermore, the electric motor can start the internal combustion engine by means of the timing device. In this case, torque is introduced into the timing drive. In contrast to most of the starter motors used, this starter motor is always connected to the internal combustion engine by means of the timing device (no decoupling and coupling), as a result of which there is less wear of the starter motor. Due to the other functions of the electric motor, which may be varied, the fact that it also constantly runs is not disadvantageous.

Furthermore, according to one variant, it is also possible for the electric motor to be operated in generator mode during predetermined operating situations of the timing drive and so to give off energy. This energy can, for example, be fed into the vehicle electrical system. If applicable, batteries and storage elements can also be charged. Idle running situations or braking situations of the internal combustion engine can be considered for the operational situation. The total efficiency can also be increased by better utilization of the motor and possibly also by additional storage.

A further method variant provides for the electric motor to bring about torque support for the internal combustion engine during predetermined operational situations of the timing drive by means of the timing drive. The torque support can also be so strong that it can be called a boost function. In particular, this can happen if the predetermined operational situation is a turbo lag of the internal combustion engine, said turbo lag transferring the transmission of the timing drive. The response characteristics of the internal combustion engine can be improved in this way.

Such torque support can, however, also be brought about if the predetermined operational situation is a stalling situation of the internal combustion engine, said stalling situation being transferred to the transmission of the timing drive. Particularly when starting the motor vehicle from rest and/or braking the motor vehicle, this achieves a meaningful advantage because the electric motor engages in a supportive manner.

One method variant provides for the control device to be developed as a regulating device in order to introduce into and/or tap from the transmission, in a regulated manner, additional torque and/or an additional torque profile depending on the at least one operational parameter. The entire control of the electric motor consequently takes place within a closed loop, so that constant polling and readjustment take place for adapting to the operational situation or to the constantly changing operational situations.

For the sake of completeness, it is also mentioned here that an essentially synchronous drive (running) of the individual components takes place in the timing drive.

Furthermore, the electric motor (electric machine) could be connected via a switchable transmission. In this way, it would be possible to operate the electric machine at rotational speeds that differ from that of the timing drive. One example that is mentioned here is a cold start at very low temperatures.

In the following, the present invention is explained in more detail using a drawing. The drawing shows:

A schematic perspective depiction of an internal combustion engine with timing chain drive.

The invention is naturally not restricted to the use of a timing chain drive; rather, a belt or gear transmission, as well as mixed forms of all transmissions, including chain drives, can also be used as the transmission.

The internal combustion engine 1 shown in the FIGURE has an engine block 2, in which a crankshaft 3 is indicated in dashed lines in the lower area and a camshaft 4 is indicated in dashed lines in the upper area. The front side of the internal combustion engine 1 is shown open, so that the view on to the timing chain drive 5 is free. The timing chain drive 5 is either arranged in a shaft on the engine block 2 or is sealed by a cover (not shown). A shaft butt 6 of the crankshaft 3 is led out of the engine block 2 at the front and a crankshaft sprocket 7 is arranged on this in such a manner that it does not twist. A shaft butt 8 of the camshaft 4 is likewise led out of the engine block 2 at the front and a camshaft sprocket 9 is arranged on this in such a manner that it does not twist.

The engine block 2 furthermore has a projecting wall section 10, through which a shaft butt 11 of an intermediate shaft 12 is stuck and on which an intermediate shaft sprocket 13 is arranged in such a manner that it does not twist. The intermediate shaft sprocket 13 has a first ring gear area 13.1 and a second ring gear area 13.2. The intermediate shaft 12 is identical to a rotor shaft of an electric motor 14 that is flange-mounted on the wall section 10. The electric motor 14 is arranged next to and to the side of the engine block.

The first and second ring gears 13.1 and 13.2 of the intermediate shaft sprocket 13 are arranged so that they do not twist with respect to one another, whereby the first ring gear 13.1 is connected to the crankshaft sprocket by means of a first timing chain 15 and the second ring gear 13.2 is connected to the camshaft sprocket 9 by means of a second timing chain 16. Due to the use of an intermediate shaft 12 and the intermediate shaft sprocket 13 with a first and second ring gear 13.1 and 13.2, a gear ratio can be achieved that leads to a more favourable sprocket size of all sprockets. In addition, the division of the first timing chain 15 used and the division of the second timing chain 16 differ, as a result of which it is possible to reduce vibrations. Both sleeve roller chains and toothed chains can be used as timing chains.

The wall section 10 is developed as a constituent of a shaft of the timing chain drive 5 or likewise covered by a front cover, so that a closed, oil-lubricated area results for the timing chain drive 5.

The electric motor 12 is connected to a control and regulation device 17 by means of the conductors 18.1-18.3. The power supply can also be effected over these. The control and regulation device 17 is mounted on a further wall section 19 on the engine block 2 and connected to the motor vehicle electronics system by means of the conductors 20.1 and 20.2. Furthermore, a sensor 21 is arranged in the area of the timing chain drive 5, said sensor 21 being connected to the control and regulation device 17 via the conductor 22. The sensor 21 is arranged in such a way that it measures the vibration of the first timing chain 15 as an operational parameter. Further sensors for registering the very wide range of operational parameters (including rotational speed, engine characteristics, etc.) can be provided and their data and signals can be forwarded to the control and regulation device 17. The control and regulation device 17 is then able to trigger, or trigger in a regulated manner, the electric motor 14 depending on the operational parameters or the operational situation.

In the following, the theory of operation and the functioning of the embodiment described above are explained in more detail.

The electric motor 14 is integrated into the timing chain drive 5 by means of the intermediate shaft sprocket 13 in such a way that it can introduce into or tap from the timing chain drive 5 torque and/or a torque profile in a controlled or regulated manner. This introduction or tapping of torque can be used for various functions. For example, the vibrations that arise in the timing chain drive can be reduced by directing induced vibrations against them, and formation of resonances can be prevented. In the depicted embodiment, the sensor 21 absorbs the induced vibrations of the first timing chain 15 for this purpose and reports this to the control and regulation device 17. As soon as the vibrations increase, torque is intentionally introduced into or tapped from the timing chain drive 5 by means of the electric motor 14, so that the vibrations are reduced again. This function optionally allows downsizing of timing drive components, as well as improvement of the cam valve lift characteristics. The data for this regulation can also be provided via the electric motor 14 and via the motor control device, or other already existing sensors, engine characteristics or control devices.

According to a further variant, the electric motor 14 can be equipped as a starter motor and can start the internal combustion engine 1. Since the electric motor 14 takes over other jobs, as well, its constant engagement in the timing chain drive 5 via the intermediate sprocket 13 is not disadvantageous.

Furthermore, the electric motor 14 can run in generator mode, so that energy can be fed into the vehicle electrical system or batteries and storage elements can be charged. Such an operational situation can particularly occur during idling or in the event of engine braking of the internal combustion engine 1.

A boost function by means of torque support is also possible. In such a boost function, the electric motor 14 introduces increased torque into the timing chain drive 4 via a certain rotational speed range, e.g., in order to compensate for a turbo lag. Similar introduction of torque can also take place in the framework of stall protection. All of the functions described above can only be carried out if the electric motor 14 can be triggered or regulated by means of corresponding registering of operational parameters or operational situations of the internal combustion engine 1.

For the sake of completeness, it is mentioned here that the intermediate shaft 12 can also be used for driving ancillary components, e.g., a high pressure pump.

In the case of this invention, priority is given to reduction of vibrations in the timing chain drive 5. At the same time, however, it is also possible to realise a number of other functions as a result of this arrangement of the electric motor 14. The connection of the electric motor 14 should be carried out in such a way that it is arranged with its stator in an area that is free of oil, while the shaft butt 11 of the intermediate shaft 12 engages in the oil chamber of the timing chain drive 5. The electric motor 14 can also be operated in surroundings containing oil. In this connection, the oil can also be used as a cooling medium.

It is also possible to use timing chain drives with two camshafts or timing chain drives without an intermediate shaft with a plurality of intermediate shafts.

The operating point of the motor and the resulting regulation strategy can possibly also be selected from the electronic control unit, e.g., by means of a LAN-BUS. 

1. A timing drive (5) for an internal combustion engine (1), comprising a crankshaft (3), at least one camshaft (4), a driven gear (7) that is connected to the crankshaft (3), at least one driving gear (9) which drives the associated camshaft (4), and a transmission that interconnects the driven gear (7) and the at least one driving gear (9), characterised in that an electric motor (14) is provided which engages with the transmission in an offset manner relative to the crankshaft (3) and the at least one camshaft (4) as well as in an offset manner relative to the associated driven gear (9) and the associated at least one driving gear (7) by means of an intermediate gear, and that a control device (17) is provided, with the aid of which the electric motor (14) can be triggered by the control device (17) in such a way that additional torque and/or an additional torque profile can be introduced into and/or tapped from the transmission based on at least one operational parameter and/or at least one operational situation of the transmission.
 2. Timing drive (5) according to claim 1, characterised in that a registering device and/or evaluation device is provided, by means of which the at least one operational parameter and/or the at least one operational situation of the transmission can be registered and/or evaluated, wherein the vibration state of the transmission is registered and/or evaluated as an operational parameter and/or the vibration situation of the transmission is registered and/or evaluated as an operational situation.
 3. Timing drive (5) according to claim 1, characterised in that the transmission comprises at least one timing chain (15, 16).
 4. Timing drive (5) according to claim 1, characterised in that the intermediate gear engages with at least one timing chain (15, 16).
 5. Timing drive (5) according to claim 1, characterised in that an intermediate shaft (12) is provided that is in an effective connection with the crankshaft (3) by means of a first timing chain (15) and with the at least one camshaft (4) by means of a second timing chain (16), wherein the electric motor (14) engages directly with the intermediate shaft (12).
 6. Timing drive (5) according to claim 2, characterised in that the intermediate shaft (12) is formed as a rotor shaft of the electric motor (14) or is coaxially connected to it.
 7. Timing drive (5) according to claim 1, characterised in that the control device (17) is developed as a regulating device and the electric motor (14) can be regulated by the regulating device in such a way that additional torque and/or an additional torque profile can be introduced into and/or tapped from the transmission in a regulated manner by the electric motor (14).
 8. Timing drive (5) according to claim 4, characterised in that the regulating device is connected to a sensor device (21), by means of which at least one signal that depends on the operational parameter and/or the operational situation of the transmission can be registered and passed on to the regulating device, wherein the electric motor can be regulated by means of the regulating device in such a way that additional torque and/or an additional torque profile can be introduced into and/or tapped from the transmission by means of the electric motor (14), depending on the operational parameter and/or the operational situation.
 9. Timing drive (5) according to claim 1, characterised in that the electric motor (14) is formed as a starter motor for the internal combustion engine (1).
 10. Method for operating a timing drive (5) on an internal combustion engine (1), in which an electric motor (14), in an offset and separate manner relative to the crankshaft (3) and the at least one camshaft (4), as well as in an offset manner relative to the associated driven gear and the associated at least one driving gear, is integrated into a transmission that interconnects the driven gear and the at least one driving gear and can be triggered by means of a control device (17) in such a way that additional torque and/or an additional torque profile can be introduced into and/or tapped from the transmission by means of the electric motor (14), wherein the method comprises the following steps: Registering of at least one operational parameter and/or operational situation of the transmission, Triggering of the electric motor (14) by means of the control device (17), in order to introduce into and/or tap from the transmission (5) additional torque and/or an additional torque profile, depending on the at least one operational parameter and/or operational situation.
 11. Method according to claim 10, characterised in that at least one operational parameter that implies the vibrations that occur in the transmission and/or that, as an operational situation, implies the vibration situation of the transmission, is registered and/or evaluated and in that the control device (17) triggers the electric motor (14) in order to introduce into and/or tap from the transmission additional torque and/or a torque profile, depending on the at least one operational parameter and/or operational situation for vibration absorption.
 12. Method according to claim 10, characterised in that the electric motor (14) starts the internal combustion engine (1) by means of the timing drive (5).
 13. Method according to claim 10, characterised in that the electric motor (14) is operated in generator mode during predetermined operational situations of the timing drive (5) and gives off energy.
 14. Method according to claim 13, characterised in that the predetermined operational situation is an idling or braking situation of the internal combustion engine (1), said situation being transferred to the timing drive (5).
 15. Method according to claim 10, characterised in that the electric motor (14) effects torque support of the internal combustion engine (1) during predetermined operational situations by means of the timing drive (5).
 16. Method according to claim 15, characterised in that the predetermined operational situation is a turbo lag of the internal combustion engine (1), said turbo lag being transferred to the transmission of the timing drive (5).
 17. Method according to claim 15, characterised in that the predetermined operational situation is a stalling situation of the internal combustion engine (1), said stalling situation being transferred to the transmission of the timing drive (5).
 18. Method according to claim 10, characterised in that the control device (17) is developed as a regulating device in order to introduce into and/or tap from the transmission, in a regulated manner, additional torque and/or an additional torque profile depending on the at least one operational parameter and/or operational situation. 